#include <stdio.h>

int main()
{
    char ch;
    char ph;

    printf("请输入一个字符：");
    scanf("%c", &ch);

    if (ch > 'a' && ch < 'z')
    {
        ch -= 32;
        printf("大写为：%c\n", ch);
    }
    else if (ch > 'A' && ch < 'Z')
    {
        ch += 32;
        printf("小写为：%c\n", ch);
    }

    return 0;
}